The present invention relates to an electron beam apparatus and, more particularly, to an absorption current image measurement apparatus suitable for sample measurement and inspection with an electron microscope.
In scanning electron microscope (SEM) inspection using an electron beam in a semiconductor process, essentially, measurements are taken for secondary electrons from a sample. However, a problem was presented that, for deep holes and trenches with a narrow width or samples with a nonuniformly charged surface, secondary electrons from the surface irradiated with a probe electron beam cannot be measured sufficiently. As prior art means to solve this problem, for example, there is a sample measurement method using absorption current, K. Yamada, et al., described in IEDM Technical Digest, 1999, pp. 483-486. According to this method, which is illustrated in FIG. 2, absorption current measurements are taken by irradiating the surface of a sample 4 with a continuous electron beam 1 and connecting a current-voltage converter circuit between the sample substrate and a ground electrode 0.